Konica Minolta SONIMAGE HS2 - 9.2 MI;TI Display Description

274
z
Denition of MI
MI (Mechanical Index) is expressed by dividing the peak-rarefactional acoustic pressure
P
r, α
calculated by con-
sidering the tissue attenuation (α = 0.3 dB/cm/MHz) by the square root of the acoustic working frequency
f
awf
(Units: MHz). This index can be expressed as follows:
MI
P
r,α
C
MI
f
awf
=
×
where
C
MI
=
1(MPa/ MHz)
z
Denition of TI
TI (Thermal Index) is the ratio of total acoustic power to the acoustic power required to raise tissue temperature
by 1 degree centigrade under dened assumptions.
TIS (Soft Tissue Thermal Index) is related to heating in abdominal, cardiac and peripheral vascular applications.
TIB (Bone Thermal Index) is related to bone heating, which may be of particular importance in fetal applications.
TIC (Cranial Thermal Index) is related to heating in cephalic applications.
z
Displayed MI/TI values
Accuracy
The MI and TI values are determined and displayed based on the measured acoustic power data. The displayed
values contain errors due to the following factors.
• Measurement errors in acoustic power measurement
• Variation in the characteristics of the system and transducer
• Ultrasound propagation characteristics
Display conditions
• If MI values are less than 0.1, they are rounded up to two decimal places for display, and MI values of 0.1 or
greater are rounded up to one decimal place for display.
• TI is displayed to one decimal place.
9.2 MI/TI Display Description